Government regulations in most countries require wireless devices to transmit signals within defined frequency bandwidths for a particular channel. With an ever-increasing demand for usage of wireless devices, many governments are shrinking the frequency bandwidths allowable for each channel. For instance, in the United States, the Federal Communications Commission (FCC) has reduced the public safety channel bandwidth for mobile radios from 25 KHz to 12.5 KHz with future plans to allow 6.25 kHz channel spacing. With the reduction of channel bandwidths, it has become ever more critical that each radio transmit information at accurate modulation frequencies within the maximum tolerated channel bandwidths.
Frequencies produced by radios are derived from crystals driving voltage controlled oscillators within the radios. The accuracy of the frequencies produced by the oscillators tend be affected by temperature, humidity, voltage, and a number of other factors. Such factors tend to cause the frequencies produced by the oscillators to drift over time. As a result of this frequency drift phenomenon and in light of narrower bandwidths requirements, radios need to be serviced and recalibrated more often to ensure they are operating within tolerated bandwidths.
Calibration involves removing the radios from operation and bringing them in for servicing. With larger demand for calibration maintenance due to the more stringent requirements for narrow bandwidth channels, the quantity of qualified personnel and centers able to perform these calibrations is limited. Consequently, radios can be subject to long periods of removal from operation while they are waiting to be serviced as well as an increased cost of maintenance to the user community.
Servicing involves connecting the radios to expensive calibration and test equipment and performing a large amount of manual processes that require well-educated service technicians. These manual processes tend be slow, tedious, and are prone to errors.